“the supreme problem solver of the 20th century“ (Freeman Dyson) Dr. Adriana Banu Department of Physics and Astronomy (JMU) Harrisonburg, Virginia, USA 1 Hans Bethe’s Scientific Work “If you know his work, you might be inclined to think he is really several people, all of whom are engaged in a conspiracy to sign their work with the same name.” - John Bahcall (1934-2005) American astrophysicist 2 78 Years of Scientific Publication • Born: July 2, 1906 - Died: March 6, 2005 Nearly 400 publications, including several books: • First publication: 1924 (aged 18) – with A. Bethe and Y. Terada – “Experiments Relating to the Theory of Dialysis” – Zeitschrift f. Physik. Chemie, 112, pp. 250-269 • One of his last few publications: 2002 (aged 96) – with G. C. McLaughlin, R.A.M.J. Wijers and G. E. Brown – “Broad and Shifted Iron-Group Emission Lines in Gamma-Ray Bursts as Test of the Hypernova Scenario” – Astrophys. J., 567, 454-462 3 Topics of Bethe’s Publications Atomic physics and spectroscopy Interactions of fast particles with matter (scattering, annihilation, pair creation, …) Solid state physics Hydrodynamics, especially shock waves Nuclear physics (from ‘pure’ physics to bombs) Nuclear astrophysics (stellar energy, supernovae, and solar neutrinos) Nuclear weaponry, the arms race, and national security Energy policy, including fission power Gravitational wave sources (evolution and merger in binary star systems) 4 5 Quantum Theory and Special Relativity 1900 1905 6 Rutherford, Bohr, and the Hydrogen Atom 1911 1913 7 The Old Quantum Theory 8 Bohr, Sommerfeld, & the Old Quantum Theory 9 Birth of Quantum Mechanics (1924-1928) (left to right: de Broglie, Schrödinger, Born, Heisenberg) 1924 1926 1927 10 11 Growing Up (1906-1924) • Born July 2, 1906 in Strassburg, Germany (now Strasbourg, France) • His father was a Privatdozent of physiology at University of Strasbourg • His mother was an accomplished musician (also had a Jewish heritage!) • As a child Hans Bethe was “off-scale” (he started reading at the age of 4 and began writing in capital letters, by the age of 5 he fully understood fractions and could add, subtract, multiply, and divide any of them) • As a young teenager Hans Bethe would go to his father’s laboratory and help with various chores 12 • His family moved to Frankfurt where Hans Bethe attended the Goethe Gymnasium from 1915 to 1924 Bethe’s Education & First Academic Jobs (1924-1929) • University of Frankfurt, 1924-1926 – Hans studied physics with Walter Gerlach and Karl Meissner, who encouraged him to move on to the University of Munich. • University of Munich, 1926-1928 – Hans studied with Arnold Sommerfeld. – His doctoral thesis analyzed the diffraction of electrons by crystals. – Published it in Ann. Phys. 87, 55-129 (1928) – “Theory of the Diffraction of Electrons by Crystals” • University of Frankfurt and then Technical College of Stuttgart (one semester each as an instructor), 1928-1929 – The crystallographer Paul Ewald invited Bethe to Stuttgart as his assistant. 13 – Sommerfeld recalled Bethe to Munich in the autumn of 1929. “Calculation of Electronic Affinity of Hydrogen” (Zeitschrift für Physik 55, 815-821 (1929)) “The old quantum theory was unable to calculate the binding energy of a second electron to the hydrogen atom; in fact, two authors concluded that a negative hydrogen ion could not exist at all […] I use the variational method pioneered by Hylleraas […] and thus find the binding energy of the extra electron […] = 0.73 eV. […] It is shown that there are probably no discrete excited states of the H- ion.” −excerpt from the abstract 14 “The Theory of the Passage of Swift Corpuscular Rays through Matter” Ann. Phys. 5, 325-400 (1930) “The inelastic collision of a fast charged particle (electron, proton, α-particle) with an atom is treated according to Born’s theory of wave mechanics. […] The theory is developed in detail for collisions of hydrogen atoms and, in as far as possible, for complex atoms. […] The agreement of this theory with experiment is satisfactory to good.” −from the abstract Leading to the famous Bethe-Bloch formula! 15 Bethe’s Rockefeller Foundation Traveling Scholarship (supervisors: Ralph Fowler in Cambridge and Enrico Fermi in Rome) 1931 16 “The best thing in Rome is unquestionably Fermi. It is absolutely fabulous how he immediately sees the solution to every problem that is put to him, and his ability to present such complicated things as quantum electrodynamics simply […] I am now actually sorry that I cannot stay here longer, or as the case may be, that I did not come here for all of the Rockefeller-time.” −excerpt from a letter addressed to Sommerfeld (1931) 17 Back to Rome (1932) • Bethe and Sommerfeld wrote a review article “The Electron Theory of Metals” for the Handbuch der Physik. This article became famous in the physics community – it covered the basis of what is now called solid state physics. • Also for the Handbuch der Physik Hans Bethe wrote another review article “Quantum Mechanics of One- and Two-Electron Problems” which became the presentation of quantum mechanics (nonrelativistic and relativistic) from which an entire generation of physicists learned how to address the problems of immediate relevance to experimentalists during the “In 19311930s. Fermi was completely a theoretical physicist. But in 1932 while he was still doing theoretical work, he was determined to go into experimental nuclear physics” – from a letter that Hans Bethe wrote to Sommerfeld (April 20, 1932) 18 Chadwick’s Discovery of the Neutron (1932) 19 Bethe’s Dismissal from University of Tübingen • During the winter of 1932-1933, Bethe was Acting Assistant Professor at the University of Tübingen, where Hans Geiger, the Professor of Experimental Physics, was his supervisor. • In late January 1933, Hitler became Chancellor in Germany • In April 1933, Hans Geiger summarily dismissed Bethe from his teaching position at Tubingen. (Bethe’s mother was Jewish.) • Sommerfeld invited him back to Munich and worked hard during the summer of 1933 trying to find jobs for Bethe and other displaced academics. 20 Emigration to Great Britain (1933) Academic Positions in Manchester and Bristol (left to right: Bethe, Genia and Rudolf Peierls, Neville Mott) 21 “Quantum Theory of the Diplon” (with R. Peierls) Proc. Roy. Soc. London Ser. A148, 146-156 (1935) “The diplon is the heavy isotope of hydrogen, now called deuteron. It is the simplest composite nucleus […] The photoelectric disintegration of the deuteron is calculated; this, in fact, was the origin of the paper: James Chadwick who (with Maurice Goldhaber) had observed the photo-disintegration, challenged the authors to give a theory of the process” -Bethe’s commentary from “Selected Works of Hans A. Bethe” (1996) 22 The “Neutrino” (with R. Peierls) Nature 133, 532-533 (1934) “The authors show that it would be very unlikely that free neutrinos can be observed: Bethe and Peierls could not foresee that there would be nuclear reactors giving neutrino fluxes enormously greater than the radioactive sources available in 1934. Using these, Reines and Cowan (1956) were able to observe free neutrinos, work for which Reines received the Nobel Prize in 1995. Nor could they foresee accelerators giving protons of energies of TeV which produce similarly large neutrino fluxes.” -Bethe’s commentary from “Selected Works of Hans A. Bethe” (1996) 23 Becoming Bethe Arnold Sommerfeld (1868-1951) “If you were not to find satisfaction in the search for knowledge, you would Thoroughness despairingly put your hands in your lap Clarity & and say: It is too difficult for us humans.” & Rigor Albrecht Bethe, 1899Simplicity 24 Coming to the United States (1935) After spending Fall 1934 at the University of Bristol, he accepted a job as an assistant professor at Cornell University in Ithaca, NY. Cornell University would be his home institution for the next 70 years. 25 “The Happy Thirties” Assistant Professor Bethe with Cornell physics colleagues in 1935 26 Bethe, Livingston and Bacher: Three Musketeers of Nuclear Physics at Cornell 27 “Bethe’s Bible” In 1936-37, Bethe published three long articles in the journal Reviews of Modern Physics: • Nuclear Physics. Part A, Stationary States of Nuclei (with R. F. Bacher; 146 pages) • Nuclear Physics. Part B, Theoretical Nuclear Dynamics (175 pages) • Nuclear Physics. Part C, Experimental Nuclear Dynamics (with M.S. Livingston; 145 pages) These three articles, totaling 487 pages, amounted essentially to a compendium of everything known in nuclear physics at the time – collectively they became known as “Bethe’s Bible.” 28 George Gamow and Edward Teller 29 Fourth Washington Conference on Theoretical Physics: Stellar Energy and Nuclear Processes (March 21-23, 1938) 30 Proton-proton reactions and the CN cycle: two sets of reactions that convert hydrogen into helium within stars 31 “Energy Production in Stars” (Phys. Rev., 55, 434-456, 1939) “[…] the most important source of energy in ordinary stars is the reactions of carbon and nitrogen with protons. These reactions form a cycle in which the original nucleus is reproduced […].Thus carbon and nitrogen merely serve as catalysts […]” − from the abstract Nobel Prize in Physics (1967) 32 The 1967 Nobel Prize for Physics “Professor Bethe, you may have been astonished that among your many contributions to physics, several of which have been proposed for the Nobel Prize, we have chosen one which contains less fundamental physics than many of the others and which has taken only a short part of your long